24 



Irrigation and Drainage 



From these figures it appears that while more water was lost 

 in the field, for each pound of dry matter produced, than in the 

 pot experiments, the amount of water used per square foot in 

 the pots was in every case much greater than it was in the field. 

 So, too, were the yields of dry matter, when expressed in 

 units of equal areas, much greater in the pots than they were in 

 the field. These relations are very suggestive, though, of course, 

 not at all demonstrative, that the larger amount of water used 

 per unit area in the pot experiments is to be credited with the 

 larger amount of dry matter produced per unit area. The differ- 

 ences are certainly in the direction we should expect if water 

 plays the important part we have attributed to it, and if in the 

 field experiments the several crops did not have all of the water 

 they might have used to advantage. 



In 1892 pot experiments similar to those described were con- 

 ducted with barley, oats, corn, clover, and field peas, using gal- 

 vanized iron cylinders 18 inches in diameter and 42 inches deep, 

 placed in the field, surrounded by the field crop, and each experi- 

 ment being in duplicate. The results of these trials are given in 

 the table below: 



Table showing the amount of water used in producing a pound of dry matter 

 in Wisconsin in 1892 



Dry matter Water per Ib. of Computed yield Water 

 produced dry matter per acre used 



LBS. 

 .576 



.3322 



.5657 

 .5977 



.3252 



LBS. 

 375.21 



525.59 



238.22 

 398.15 

 564.43 



477.37 



LBS. 

 14,196 



8,189 

 19,184 

 12,486 



8,017 



23.52 



19 



25 



29.73 



16.89 



If, now, we express the relation between the amount of dry 

 matter produced and the number of inches of water used in these 

 trials and in those of 1891, it will be seen that the yields of dry 



